In various stages of assembly of various parts and equipment, particularly for large trucks, automobiles, construction machinery, aircraft, or the like, it is often necessary for workers to paint a large object in a containment structure commonly known as a paint booth. Although a variety of paint booth structures have been devised to effectively employ various air flow design characteristics in order to reduce paint booth operating costs while maintaining adequate paint finish quality, in the various prior art paint booth designs known to us, the paint booth operations have resulted in a large quantity of paint contaminated air filters which must be safely and legally handled and discarded. Coating overspray in a typical paint booth might be as much as fifty percent (50%) or more of the volume of coating which adheres to the object being sprayed. With increasingly stringent environmental laws, many paint contaminated filters have had to be handled as hazardous waste, and where such handling is required, a premium has been paid to dispose of such filters in hazardous waste landfills. In particular, the U.S. Environmental Protection Agency, and the environmental agencies in various U.S. states and in other nations, have promulgated regulations and strict standards which require testing and rigorous documentation for land disposal of paint loaded filters which have been produced as a result of paint booth operations.
Collection of overspray paint from a spray booth is generally achieved now by (a) use of paper type filters, (b) use of fiberglass type filters, and (c) use of a water spray curtain for knockout of paint particles to a circulating water bath. Both paper and fiberglass filters result in paint saturated filters which must pass a "paint filter test" showing the absence of free liquids, before being disposed in a landfill. Typically, such filters must be disposed, at relatively high cost, in a hazardous waste landfill. Also, wet spray booth designs result in creation of a sludge, which must be periodically removed, treated, and disposed, often by shipment to a hazardous waste landfill.
In spite of the various schemes which have so far been offered to the marketplace to reduce airflow, limit overspray, or to enhance paint filter life, a continuing and growing demand exists for a simple, inexpensive method which can be used to preserve and enhance the life cycle of paint filters, thus reducing disposal costs. The need for an improved method for paint booth operation is especially seen in conjunction with work where large mobile objects are to be painted, such as heavy haul trucks, rail cars, construction machinery, or large commercial aircraft. As will be evident to those familiar with paint booths and to whom this specification is particularly addressed, a novel filter and a method of using the filter which effectively eliminates the necessity of disposing of large quantities of spent paint filters, would be of great benefit in increasing the profitability of manufacturing plants which are now incurring large and continuing expenses with presently used filters and methods of paint booth operation.